Hybrid golf club

ABSTRACT

A hybrid golf club having a hollow club head construction including a lightweight composite core inserted into a club head cavity and juxtaposed against a front face by compressed gas to provide support to the front face therein. The core material is less dense and having greater flexibility than the front face. The front face has a variable stiffness so as to create a variable Coefficient of Restitution (COR) across the face, therein normalizing the hitting area over a greater portion of the face. The composite core supports the front face to provide a COR from about 0.8 in the middle of the face to about 0.9 in the outer section. The body of the club head has at least one opening wherein the composite core is visible and provides the shell for that portion of the club head. The composite core comprises a plurality of unidirectional layers with horizontal oriented layers alternating with vertical oriented layers to provide extra strength.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation-in-part of co-pending U.S.patent application Ser. No. 10/606,317, filed on Jun. 25, 2003,

FIELD OF THE INVENTION

This invention relates to a hybrid golf club having a hollow golf clubhead with a composite core.

BACKGROUND OF THE INVENTION

The desire for perimeter weighting in a golf club iron is well known inthe art. This desire stems from the fact that as the mass of the club isdistributed towards the perimeter, the trajectory of the hit ballbecomes more accurate, despite off-center hits away from the sweet spotof the golf club face or hitting surface. Consequently, many modern golfclub irons have a rear cavity that extends towards the rear side of theface surface of the iron. The weight saved, by creating a rear cavity inthe club, is re-distributed to the perimeter of the golf club head, andthe greater the volume of the cavity, the greater the amount of mass ofmetal that can be redistributed to the perimeter of the golf club head.

Conventionally, golf club heads were made from a single material,usually stainless steel for some metal woods and iron type clubs, andrecently a large shift in the use of titanium for metal woods. Carbonfiber composite materials have been introduced in an effort to decreasethe weight of the golf club head while subsequently increasing the clubhead's volume. Composite materials have been used widely to reinforcethin club faces, while providing ‘feel” and in some instances vibrationdampening.

Typically, in an iron club head, composite inserts are used to supportthe rear surface of the front face. They are generally sheets ofcomposite attached with an adhesive. The lightweight composite allowsfor the face to be thin and therefore a larger face and bigger sweetspot.

It is desirable to provide a golf club that optimizes the moment ofinertia (MOI) and also normalizes the ball speed over a large area ofthe face. Thus the ball is launched at similar speeds over a largeregion to create a larger sweet zone.

SUMMARY OF THE INVENTION

The present invention is directed to a golf club having a metal bodywith a hollow composite core structure. The body is made of a firstmaterial having a front face of variable stiffness and a rear cavity.The composite core is of a lower density than the body and includes aportion juxtaposed with the front face for support.

In one embodiment of the invention, a composite core and metallic bodyare combined to form a hollow golf club head. The composite is used tostructurally support a thin front face, and for increased Coefficient ofRestitution (COR). Preferably, the front face is of a higher density andlower Young's Modulus than the composite core.

In an embodiment of the invention the front face has a first stiffnessat the center of gravity (near the center of the face) and becomesprogressively more flexible away from the center of gravity. Preferably,the club is designed such that the face provides substantially uniformball speed from hits at various locations, i.e., an enlarged sweet zone.The COR across the front face varies from about 0.8 to about 0.9 acrossthe front face. The variation in flexibility across the face may be aresult of the front face structure alone, or it may result from acombination of the front face and composite core structures or the frontface and composite core materials. The internal volume of the golf clubiron head is about 35 cc to 50 cc.

An embodiment of the invention is comprised of a metal body member thatmay be cast, forged, stamped or made by metal injection molding. Thebody member is placed in a mold and a composite core is biasly inflatedand expanded against the metal body and mold by a bladder method.Preferably, the composite core is located such that the compositematerial is juxtaposed against portions of the metal body and mold. Themold is used as a boundary for specific regions of the club head wherethe metal body has an opening(s) such that the exterior of the club ispartially metal and partially composite. Embodiments of the inventionmay be provided in both hollow irons as well as metal woods.

The composite core is made up of a plurality of carbon fiber layers,preferably six, each layer is unidirectional, and horizontal orientedlayers alternate with vertical oriented layers to provide strength.

The club has a port in the sole for the introduction and removal of abladder material. This port houses a plug, preferably a heavy materialsuch as tungsten which has a density greater than 14 g/cc³. The extraweight in the sole is allowed by the removal of weight in the body,especially in the front face which may be very thin because of thelightweight composite core backing. The weight placed in the soleprovides for increased peak trajectory.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a rear view of the hybrid club of the present inventionshowing the exposed bladder molded composite core.

FIG. 2 is a sole view showing the plug position.

FIG. 3 is schematic toe view showing the center of gravity for aTitleist® Model 503-H 22° of the present invention in relationship to aconventional 3 iron, such as a Titleist® Model 804.

FIG. 4 is a cross-sectional view along line A-A of the invention of FIG.1 showing the bladder molded composite core

FIG. 5 is a schematic showing the six layers of carbon fiber that formsthe composite core.

FIG. 6 is a bar chart indicating potential carry distance.

FIG. 7 is a bar chart indicating peak trajectory height and rolldistance.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of an iron golf club head 10 of the present invention isshown on FIGS. 1 to 5. The body 12 of the golf club head 10 has a metalportion having a front face 16 for striking golf balls, a top section15, a sole 17 having an open port 19, a hosel 21, and a rear opening 25.A sole plug 26 is inserted within the port 19, as discussed later. Thebody 12 has a cavity 22 that is defined rearward of the face section 14.A lightweight composite core 20 is biasly placed within the cavity 22,juxtaposed against a rear surface 18 of the body 12, to internallyreinforce the body 12, and also support the front face 16. The compositecore 20 preferably has a composite structure made-up of a plurality ofunidirectional carbon fiber layers, preferably six layers, with thehorizontal direction fibers alternated with the vertical directionfibers for optimum strength. The metal body 12 may be cast, forged,stamped or made by a metal injection molding method, preferably the headis cast from 431 stainless steel. Reinforcing the body 12 with thelightweight composite core 20 allows for the body 12 to be thinned downin select regions. The thinned down regions permit the mass distributionoptimization (Center of Gravity and Moment of Inertia) of the club head10, and also stiffening the front face 16 that may be relativelyflexible due to the thin structure, and therein allows for weightdistribution and also dampening of vibrations which helps to createsolid feel.

The front face 16 can be made relatively thin because of thereinforcement of the composite core 20. The thickness (t1) of the frontface 16 is preferably in a range between about 0.04 inch to 0.12 inch,and more preferably, between about 0.06 inch to 0.1 inch, while thethickness (t2) of the composite core 20 is preferably between about 0.02inch to about 0.1 inch. The composite reinforced front face 16 can bedesigned to provide face flexibility characteristics that yield maximumCoefficient of Restitution (COR) values from about 0.8 to about 0.9. TheCOR of the club head 10 may vary across the front face 16 to normalizeball speed and provide an enlarged sweet zone for added forgiveness.Therein the COR of the club 10 of the present invention may be about 0.8at the face center and greater than 0.8 away from the face center.Generally, the stiffness of the front face 16 is greatest at the facecenter, and becomes progressively more flexible away from the facecenter. The coefficient of restitution is obtained under testconditions, such as those specified by the USGA. The standard USGAconditions for measuring the coefficient of restitution is set forth inthe USGA Procedure for Measuring the Velocity Ratio of a Club Head forConformance to Rule 4-1e, Appendix II available from the U.S.G.A.

The club head 10 forms a hollow style club 10 with thin walls in selectregions, especially the upper 14 a and lower 14 b regions of the faceside 16. The composite core 20 may be made of plastic, carbon graphiteor any lightweight material with a density less than 4.5 gm/cc, and maybe inserted into the hollow golf club 10 in a variety of methods. Whilethe method of inserting the composite core 20 may vary, the bladdermethod is preferred. In this method, a composite core 20 composed of acarbon fiber pre-preg material that is cut into face, body and rearlay-up pieces are pressurized by a bladder (not shown) that is insertedinto the cavity 22 through a port 19. The bladder is preferably madefrom latex, silicone, or similar materials. Preferably, the compositecore 20 is located such that the composite material is juxtaposedagainst portions of the metal body 12 and the mold. The assemblycomprises, the metal golf club body 12, composite core 20, and bladder.When positioned in a mold, which is not shown, the composite core 20 isused as a boundary for specific regions of the club head 10 where themetal body 12 has an opening, such as the rear opening 25. Thus, theexterior of the resultant club head 10 is partially metal and partiallycomposite. A source of pressurized gas, usually air, (source not shown)is introduced through the port 19 to inflate and expand the bladder, andthereby cause plies of the composite core 20 to biasly expand againstthe inner walls of the golf club 10 and against the internal walls ofthe mold. The internal walls of the tool are used as a boundary for aregion of composite or plastic that is visible to the outside of thegolf club 10. Heat may be provided at a predetermined temperature for aselected period of time, i.e., a time sufficient to allow proper curingof the composite material, which for an embodiment of the invention ismaintaining the club head 10 in a mold for about 30 minutes, at apressure of about 50 psi and a temperature of about 275° F. Afterdepressurizing, the bladder may be removed through the port 19, and thegolf club head 10 may be removed from the mold. The exterior of theresultant club head 10 is partially metal body 12 and partiallycomposite core material 20 with an internal volume between about 35 ccto 50 cc. Upon removal from the mold, the head 10 has molding residueremoved and the perimeter of the club head 10 is sanded smooth and thepolished for a final scratch finish. The rear piece of the compositecore 20 has a clear coat applied and artwork is performed with a laseralignment fixture prior to a lacquer applied to the face and a solenumber painted thereon to finish the head.

The introduction of the plug 26 in the port 19 causes the center ofgravity of the club head to be lowered. Plugs 26 of varying weight canadjust the swing weight of the club to match a golfer's specifications.An embodiment of the invention used a plug 26 made from tungsten with adensity of about 14 g/cm³.

FIG. 3 illustrates the relationship of the center of gravity of aTitleist® Model 503-H, 22° loft hybrid iron of the present invention,and a Titleist® Model 804, 3 iron, which would be the iron closest inspecification to the hybrid club. The center of gravity of the hybridModel 503-H is lower and further rearward than the 3 iron. This willmean greater distance and greater peak trajectory which translates intoa better “drop and stop”™ performance. The Model 503-H with about a 22°loft will yield a ball backspin of less than 5000 rpm at a ball speed ofabout 126 mph at a launch angle of about 14°.

Performance test data utilizing the swing characteristics of the“Average Tour Player” is available for the Model 503-H hybrid ironsagainst conventional iron clubs. FIG. 6 is a chart depicting the carrydistance of the average tour player for various irons and fairway woods.The Model 503-H hybrid with a 22° loft would fall between the 3 and 2irons with a carry distance of 221 yards versus the 217 yards expectedwith the 3 iron and 224 yards with the 2 iron. The Model 503-H hybridwith a 19° loft will deliver 229 yards versus 224 yards for a 2 iron and234 yards with a 19° fairway wood. FIG. 7 correlates the data from FIG.6 and what it means as to peak trajectory height and roll distance.

The hybrid design offers a hollow construction, wide and low bounce solefor a more forgiving club than a traditional long iron, thin front facesupported by the composite core, a lowered and further back center ofgravity improves launch angle and spin, all of which makes for an easierto hit golf club than the traditionally designed long irons. Thesehybrid clubs are designed as an easier hitting alternative to the 2, 3and 4 irons and/or 3, 4, 5 and 7 fairway woods depending on individualpreferences.

The construction of the club head 10 can comprise a variation in thethickness of the front face 16, in which the front face 16 is preferablypartitioned into oval regions, each having a progressively lowerstiffness. Thus, moving away from the face center, the front face 16decreases in stiffness and thus increases in flexibility, thereinincreasing the COR in that area. This design normalizes ball speed overa large range, thus improving the golf club's “forgiveness” or enlargedsweet spot. The front face 16 may be made such that it's flexibility inthe face center (proximate the location of the CG) is generally stifferthan the area around the face center. The increase in COR in combinationwith the energy loss, that occurs from missing a direct central hit onthe front face 16, balances out to thereby give the same ball speed as ashot hit directly in line with the face center. While it is known thatvariable face flexibility can be achieved by making adjustments in thethickness of the front face 16, an example of the invention accomplishesthe varying of flexibility by incorporating a varying compositestiffness (via geometry or material variations).

It is believed that those skilled in the pertinent art will recognizethe improved inventive concepts of this invention. And they will readilyunderstand that while the present invention has been described inassociation with a preferred embodiment thereof, and other embodimentsillustrated in the accompanying drawings, numerous changes,modifications and substitutions of equivalents may be made thereinwithout departing from the spirit and scope of this invention.

1. A golf club head comprising: a body made of a first material having afront face of variable stiffness, and a rear cavity extending rearwardfrom the front face; a composite core comprised of a second materialless dense and more flexible than the first inserted into the rearcavity; the composite core comprising a plurality of unidirectionalcarbon fiber layers, with horizontal direction layers alternating withvertical direction layers; the composite core inflated and expanded by apressurized gas wherein at least a portion of the composite core biaslyjuxtaposes against the front face to form a hollow body having aninternal volume between 35 cc to 50 cc.
 2. The club head of claim 1,wherein the composite core is made from a lightweight material such ascarbon graphite.
 3. The club head of claim 2, wherein the composite corematerial has a density equal or less than 4.5 gm/cc.
 4. The club head ofclaim 1, wherein the plurality of layers is six.
 5. The club head ofclaim 1, wherein the stiffness of the front face is greatest at the facecenter, and becomes progressively more flexible away from the facecenter.
 6. The club head of claim 1, wherein the Coefficient ofRestitution varies across the front face to normalize ball speed andprovide for an enlarged sweet zone.
 7. The club head of claim 5, whereinthe maximum Coefficient of Restitution, ranges between about 0.8 toabout 0.9.
 8. The club head of claim 1, wherein the pressurized gas isair.
 9. The club head of claim 1, wherein the rear cavity comprises anopening that is sealed by a visible portion of the composite core. 10.The club head of claim 1, wherein the elasticity of the material of thecomposite core may cooperate with the front face to create a varying CORacross the front face for normalizing ball speed and creating anenlarged sweet zone.
 11. The club head of claim 1, wherein the body iscast from 431 stainless steel.
 12. The club head of claim 1, wherein thebody comprises a sole having a port defined therein for housing a plug,the plug having a density heavier than the body.
 13. The club head ofclaim 11, wherein the plug is made form a tungsten material having adensity greater than 14 g/cc³.
 14. The club head of claim 1, wherein thefront face includes a loft of about 22° and a ball backspin of less than5000 rpm when the ball exhibits a speed of about 126 mph at a launchangle of about 14°.